Various types of X-ray apparatus have been used in the past for the inspection of tires to discover defects not visible from viewable portions of tires. For the most part, such apparatus has been associated with automotive servicing or with the manufacture of tires. Apparatus installed in service stations and tire retailers are usually adapted for inspection of tires which are mounted on wheel rims for the discovery and location of defects incurred in use of the tires on the road for subsequent repair. In the tire manufacturing environment, tire makers universally use X-ray apparatus for quality control purposes to discover manufacturing defects.
In trucking operations involving medium and large trucks, it is a standard practice to recap or retread tires after a period of use in which the original tread is worn away. The reason for this is simple: medium and large truck tires are relatively expensive. In most cases, little damage occurs to truck tires in normal use such that the tires can be safely retreaded if undamaged tire carcasses are used. On the other hand, when a tire with defects is recapped, the tire can be completely destroyed under the pressures and temperatures which occur during normal use creating hazards to the driver and others on the road. A problem arises in determining if a tire carcass has been damaged in a manner that cannot be discerned by visual inspection of the carcass. While large punctures and damage to the rubber portions of a tire can often be found by visual inspection, small punctures and damage to the tire cords are not usually visible externally.
The hazards to humans from overexposure to penetrating radiation, such as X-rays, are more fully appreciated in current times than they were in the past. Thus, while various types X-ray apparatus for tire inspection in general automobile and specialized tire servicing establishments have been proposed, such apparatus is not in general use at present because of the need to provide specialized training to infrequent operators of such equipment, the expense of acquiring and maintaining such equipment, and the liabilities involved. In contrast, quality control and product liability prevention in tire manufacturing require that newly manufactured tires be closely inspected. Since X-ray inspection of tires in such a setting is an ongoing operation, the expense of the necessary equipment and the training of personnel can be more easily justified. As a result, the development of industrial tire X-ray equipment has continued while the development and availability of similar equipment suitable for small commercial users has lagged.